They're not paying for Dropbox, they're paying for the millions of people who use Dropbox.

Correct.

They already have AirDrop. When not exactly the same, Dropbox compete in a similar way but using Cloud and with no operating system limitations. Dropbox is even available for Linux, with or wiithout GUI.

As for the article, well companies buy others all the time and it doesn't necessarily mean that they will then get rid of them... sorry, silly me, it's the "Apple" thing again, you must love or hate them... can't we actually lose the irrational stupidity of the Apple haters vs lovers, it's long past being even boring...

Edit: Ah well, I see that was a waste of time just by looking at the next post...

The bigger, and to me more likely, risk is that Apple will buy up Dropbox, incorporate it into iCloud and then kill it off for everyone else.

That makes no sense, at least, not to me.

There are a lot of Windows users which own iPads too. "Killing" the service for other operating system will only affect the main functionality of the software, which is for sure the main advantage here: ability to copy and move stuff between devices.

that depends, if it's only compatible with Mac computers then Dropbox will be just fine in the PC and Android world

Dude, you really need to loosen your prejudice a little; I think in the above scenario Dropbox would be just fine on the Mac as well. Or do you really think that all Mac users have stopped using Skype just because FaceTime is available??

I think dropbox is holding out for money. Which makes sense; it's an extremely popular service. And it would fit well with Apple. It would also be a good fit for Microsoft. And also for Google. And for many other companies which couldn't afford it.

I'm not sure how profitable it is, though - I know tons of people who use it. But I don't know anyone who pays for it.

that depends, if it's only compatible with Mac computers then Dropbox will be just fine in the PC and Android world

As others have said, I don't think Apple will do that. It really would not be practical. It will be available on other OSes (Windows, certainly) for the same reason that iTunes is - Apple are aware that the Mac's relatively limited customer base would mean their product would be unavailable to the vast majority of users worldwide, thereby rendering it largely a failure.